Mapping prodromal psychosis: a critical review of neuroimaging studies

The onset of schizophrenia is usually preceded by a prodromal phase characterized by functional decline and subtle prodromal symptoms, which include attenuated psychotic phenomena, cognitive deterioration and a decline in socio-occupational function. Preventive interventions during this phase are of great interest because of the impressive clinical benefits. However, available psychopathological criteria employed to define a high risk state for psychosis have low validity and specificity. Consequently there is an urgent need of reliable neurocognitive markers linked to the pathophysiological mechanisms that underlie schizophrenia. Neuroimaging techniques have rapidly developed into a powerful tool in psychiatry as they provide an unprecedented opportunity for the investigation of brain structure and function. This review shows that neuroimaging studies of the prodromal phases of psychosis have the potentials to identify core structural and functional markers of an impending risk to psychosis and to clarify the dynamic changes underlying transition to psychosis and to address significant correlations between brain structure or function and prodromal psychopathology. Additionally, neurochemical methods can address the key role played by neurotransmitters such as dopamine and glutamate during the psychosis onset. To conclude, multimodal neuroimaging may ultimately clarify the neurobiology of the prodromal phases by the integration of functional, structural and neurochemical findings.